Mice Reproduction in Pet Stores

There's rather more sex than you might expect in a pet store. Angelfish stake out territories in the stock tanks and lay eggs on walls. Guppies do what guppies do, and you're never going to run out of them. Stick insects do whatever it is they do and produce multitudes of stick insects, and ferrets arrive neutered precisely so we won't be overrun with ferrets.

At Animalia, the heavy sex goes on in the back room. I'm not talking about me and David. Some days we hardly have time for a smooch, and anyway, if we started anything either a customer or a delivery van would arrive. Nothing puts a crimp in romance like a dog food delivery.

No, I'm talking about the mice. We keep breeding groups of mice, four females and one lucky, lucky male, in tanks in the back. Fresh food, water and bedding every day, and nothing to do but procreate.

Mice in Love

When we opened, David decreed that we would breed our own mice rather than buying them. I thought that was a pretty good idea. For one thing, it would help us control the cost of mice, as well as the supply. For another, if even one female mouse gets into a cage of males for as long as a nanosecond, there will be babies, and in spades if a male mouse gets into a cage of females by accident. Those little suckers are fast, and forget the romantic music, wine, roses or – and this may seem hard to believe – chocolate. Mice just get right down to business. We might as well take advantage.

Because mice are on the menu for everything from garter snakes to wolves and corn snakes to water monitors, they take the whole reproduction business very seriously indeed. Remember the Star Trek episode with the tribbles? Yeah, well, take out the purring, the cute, fluffy fur and the Klingon aversion and you pretty much have mice. (I'm not really sure about the Klingon aversion.)

About a year into the Mouse Project, we noticed that we weren't getting quite as many baby mice as we used to, and that was puzzling. In the course of nature, mice never stop reproducing unless they absolutely must. Maternity seems to have an aphrodisiac effect.

When Mama Mouse has her babies, Papa Mouse has to get those cigars out quick, because at about two that same afternoon, Mama will be ready to start another litter. Oh, yes, you could see her there, tapping her feet and looking at her wristwatch.

"Come on, Fred! I have a reproductive lifespan of two years, maximum, and the biological clock is ticking double-time!”

And Fred, dragging his tail over, bleary-eyed and haggard.

"What, again?” Fred, you see, has three other lovely and demanding wives with their own biological clocks.

Occasionally, Fred gets a new wife, and that's not as much fun as you might think, either. The first thing the girls do is make sure the new babe knows her place in the harem. Once that's sorted out, and the squeaking and bleeding has stopped, all four girls pile onto Fred and make sure he knows his place, too.

What makes mice so particularly tribbley is that they can nurse one litter while gestating a second.

By the time the first litter is ready to go forth and multiply on its own, there's another one in the wings. If baby mice slept in cribs, the sheets would never get cold. Fred doesn't get much rest.

We thought, when the reproduction rate started to drop, that the girls had caught on to what we were doing with the kids. You can tell a mom her kids are entering a fascinating career in herpetology, but she's gonna suss out the truth eventually. Really, who needs that many herpetologists?

But, in retrospect, maybe it was Fred after all. Maybe he had ambitions of his own; to watch ESPN and drink beer. Not everyone is cut out for the fabulous life of a studmuffin.